You have to think even if you are only eating 1250, your resting metabolic rate is going to be much higher than that, at least 1800 if not higher, even if you're just sitting on your butt. By doing more work you're pressuring your body by not eating enough.
On days you work out, you want to make sure you eat what you want + the calories you worked. You'll maintain your standard deficit but have a boost in metabolism.
Make sure that you are
1) Eating good healthy food like lean meat, veggies, etc.
2) Eating enough! I can't stress how important this is. Your body is smart and it knows when you are pushing it too hard. It will hold on for dear life and you'll just get worn down because you aren't losing. You must eat enough food.
3) Work out regularly but not too hard - walk more than run, lift books and heavy things in a natural way.
Best of luck. I've been fighting weight loss for almost my entire adult life + my childhood too. I didn't lose an ounce trying to stick under 1200 and I made myself miserable because I was always hungry.
Goal 1: 190 - Reached 4/3/11
Goal 2: 180
Goal 3: 170
Goal 4: 160
Goal 5: 155! LETS DO THIS